title: ox-LDL downregulates eNOS activity via LOX-1-mediated endoplasmic reticulum stress.
abstract: Vascular endothelial injury induced by oxidized low-density lipoprotein (ox-LDL) has been implicated in the early stages of the pathogenesis of atherosclerosis. In this study, we incubated bovine aortic endothelial cells (BAECs) with ox-LDL (100 µg/ml) in order to induce endoplasmic reticulum (ER) stress and to investigate the regulation of endothelial nitric oxide synthase (eNOS). Within 4 h of exposure, ox-LDL rapidly induced ER stress, as demonstrated by the measurements of proline-rich extensin-like receptor kinase (PERK) and glucose-regulated protein (GRP)78. ox-LDL induced the rapid dephosphorylation of eNOS at Ser1179 and a subsequent decrease in eNOS activity. This effect appeared to be highly specific as no change was observed in the levels of phosphorylated eNOS at Thr497 or eNOS protein. Of note, a simultaneous decrease was also observed in the active (phosphorylated) form of Akt (Thr308/Ser473), which has been demonstrated to phosphorylate eNOS at Ser1179. Further analysis indicated that Brefeldin A (BFA), an ER stress-inducing reagent, induced the rapid dephosphorylation of Akt and eNOS at Ser1179. 4-Phenylbutyric acid (PBA), an inhibitor of ER stress, blocked the ox-LDL-induced dephosphorylation of Akt and eNOS. Furthermore, JTX20, a lectin-like ox-LDL receptor-1 (LOX-1) blocking antibody significantly eliminated the ability of ox-LDL to mediate the dephosphorylation of eNOS and Akt. Our results indicate that the downregulation of eNOS by ox-LDL, as driven by LOX-1-mediated ER stress, is associated with the PI3K-Akt-eNOS signaling pathway.
authors.affiliation: Department of Biochemistry and Molecular Biology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei 430030, P.R. China.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.forename: Morad Dirhem Naji
authors.initials: MD
authors.lastname: Abid
authors.forename: Yufang
authors.initials: Y
authors.lastname: Xiong
authors.forename: Qing
authors.initials: Q
authors.lastname: Chen
authors.forename: Juan
authors.initials: J
authors.lastname: Chen
mesh_terms: D000818:Animals; D019138:Antibodies, Blocking / Q000494:pharmacology; D001011:Aorta / Q000166:cytology; D020126:Brefeldin A / Q000494:pharmacology; D002417:Cattle; D015536:Down-Regulation / Q000187:drug effects*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010654:Phenylbutyrates / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051127:Scavenger Receptors, Class E / Q000378:metabolism*
chemical_list: D019138:Antibodies, Blocking; D008077:Lipoproteins, LDL; D010654:Phenylbutyrates; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein; D020126:Brefeldin A; C075773:4-phenylbutyric acid; D052250:Nitric Oxide Synthase Type III; D051057:Proto-Oncogene Proteins c-akt; D010749:Phosphoprotein Phosphatases